The purpose of this program is to develop flow cytometry instrumentation and cytochemical techniques for automated, quantitative cytologic examinations of exfoliated epithelium of the urinary bladder, lymphocytes from lymph nodes and peripheral blood and tissue culture cells. With our present computer-interfaced flow cytometry instrument system and specially developed fluorescence acridine orange differential staining, we are able to measure DNA, RNA, chromatin structure and nuclear and cellular diameters of cells at rates of several hundred cells per second. In preliminary clinical studies carcinomas of the bladder have been successfully identified from these measurements on exfoliated epithelium in irrigation specimens.